1. Technical Field of the Invention
The present invention relates to telecommunications networks, and more particularly, to a method and apparatus for limiting communications between non-cooperating roamer ports and home location registers.
2. Description of Related Art
In the North American Cellular Network (NACN), a mobile subscriber may roam between service areas of competing vendors. Various techniques have been developed to enable a mobile subscriber to continue being provided with mobile telephone services once they have left their home service area. In a first alternative, once a mobile subscriber travels into a new mobile switching center (MSC) coverage area and turns on their mobile station for the first time, the mobile station attempts to register with the servicing MSC for the area by transmitting an associated identification number known as the international mobile subscriber identity (IMSI) number or mobile identification number (MIN). The serving MSC then communicates with the home location register (HLR) associated with the mobile station using the received IMSI/MIN number. This communication is to inform the HLR of the mobile station's new location and to receive requisite subscriber information from the HLR to provide mobile services to the newly registering mobile station.
When a call is made to the roaming subscriber, the calling party dials a cellular number associated with the subscriber and the call is routed to the gateway MSC (GMSC) corresponding to the dialed cellular number. The GMSC queries the HLR of the called subscriber for the roaming location of the called subscriber. The HLR queries the visited MSC where the called subscriber is currently located and requests a temporary routing number which is returned to the HLR and the GMSC. The GMSC uses this temporary number to route the call to the roaming subscriber. If the calling party is located such that the resulting call to the GMSC is a long distance call, the calling party will accrue long distance charges for maintaining a connection to the GMSC of the called subscriber. The called subscriber accrues similar charges when the call is routed back to their roaming location from the GMSC. In a situation where the calling party and the subscriber may be located in the same area, this creates unnecessary expenses.
In order to combat this problem, the concept of the roamer port was developed. The roamer port is a function designed to minimize the long distance charges that a calling party and called subscriber are liable for when the called subscriber is a long distance from his/her GMSC, but a short distance from the calling party. When utilizing a roamer port, a calling party dials a dedicated roamer port telephone number. This connects the calling party to a roamer port that then sends the calling party a dial tone. Upon hearing the dial tone, the calling party dials the subscriber's normal cellular telephone number. The roamer port seizes a signaling trunk to the home location register of the subscriber only for the period of time needed to retrieve a routing number for the subscriber. The signaling trunk with the home location register is then released, and a call is set up locally from the calling party to the roamer port to the roaming subscriber. Thus, the calling party incurs no long distance charges.
Unfortunately, in order for the roamer ports to be effectively utilized, there must be agreements between various service vendors to accept roamer port calls from other service vendors. The possibility exists that a calling party attaching through a roamer port of Vendor A may be attempting to contact a subscriber party having a home location register with Vendor B, but Vendor B does not have an agreement with Vendor A for setup of roamer port calls. When the billing information is collected by Vendor A and sent to Vendor B, Vendor B will refuse to pay for used resources. Vendor B would be considered a non-cooperating vendor. Thus, when the roamer port of Vendor A attempts to contact the HLR of Vendor B, service will be refused and a routing number will not be provided. This delays local paging of the called subscriber by the time involved in signaling the transaction to the non-cooperating HLR belonging to Vendor B.